Author Topic: New member looking for some suggestions...rear cylinder drops out...  (Read 75 times)

renzo750

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I picked up am 84 VT500 last fall with 25K on the clock, pretty complete and original - needed to be freshened up - seemed to be classic dirty carbs and lots general maintenance neglect...

I've went through and brought all the maintenance up to date, cleaned the carbs, fresh gas, plugs, fluids, etc...but...

I started out this spring and rode about 10 miles - bike ran PERFECT.

All smiles I stopped to top of the tank with non-oxy and it dropped to one cylinder - then came back on, then off, etc.

Seemed like fuel issues - tank vent, gunk, obstructions, etc...however in line fuel filter seems clean with good flow.

Played with it and figured out that my rear cylinder plugs where wet with no spark. It runs and blows fuel vapor out of rear cylinder... I'm getting gas :) - To Much?  Fouling plugs to no spark condition?

New plug wires - SPARK!  Ran good for a couple blocks - cylinder drops out, comes back, drops out...

Bench test coil...seems OK, but I've been done this path before on other bikes and went ahead and replaced the rear cylinder coil with a new Rick's coil...much bright spark!

Ran good for a couple blocks - cylinder drops out, comes back, drops out...doesn't come back (a few miles)

Check - no rear cylinder spark - wet plugs.  (was not the coil or plug wires it seems)

Ignition igniter - CDI box (seems unlikely) - back to fuel issues? 

I could really use some knowledgeable suggestions help to sort this out ...bike runs great when it runs "right" 

My next step is to look at all the electrical connectors and run a few wire continuity tests... the on again off again thing is always  (at least for me) a diagnostic nightmare.

At this point I have a very fresh bike - new tires, brakes, all fluid's, clean carbs, rebuilt vacuum petcock, good body work ...can't stop now :) 

I've restored many British bikes over the years, even built a Triton but am pretty new to the nuances of Japanese "modern" electrical troubleshooting and CV carbs.

Thank you in advance for any ideas you may have.
Jim

J6G1Z

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Typically the VT Ascots suffer from fouled carbs & coil issues. The coils receive too much heat mounted above the engine.

The rear carb has a larger main jet than the front carb. Think that might be the only difference.

Are you aware of the Yahoo VT500FT Ascot Owners Group: https://groups.yahoo.com/neo/groups/ascotvt500enthusiasts/info

The moderator of that group is pretty sharp. It has been a while since I've owned a VT.

Good luck
J.

PS. This happened to me once: http://ascot500.com/index.php?topic=340.msg1702#msg1702

renzo750

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Thank you....it seems like it almost has to be something along those lines...it will be next week before I get an evening to start checking connectors and looking for that needle in a wire nest  :D
 

J6G1Z

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If I recall correctly... There was a white plastic wire plug that I had disconnected & then plugged back in. Apparently the pins inside didn't line up correctly & the pin was pushed out the back of the plastic plug. They were the leads to one of the coils. Without a VT Ascot for me to look at right now, that's about the best I can do.

J.

Bucko

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I was seeing something similar on my Ascot when I bought it.  The classic Ascot problem, which is related to bad coils, was a no-hot-start condition, i.e. ride the bike for a while, stop for fuel, won't restart until it cools down.

My problem was different: when it got hot, the bike would stall when coming to a stop, but would restart no problem - next stop, stall again!  I went looking at all the usual suspects but couldn't find anything wrong.

At one point, I decided to replace the wiring harness as a PO had taken some liberties with cutting some wires (nothing to do with ignition system) so basically every connector on the bike was disconnected/reconnected.  After that my hot stall issue was gone (fingers crossed - I haven't had a stall for a few years).  I suspect the connection to the igniter(s) was funky and disconnecting/reconnecting the connector cleaned things up.

renzo750

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Thank you - I ran out of time last night but I did see some questionable wires near the igniter connector over the coils - I'm going to detail that area of the harness as soon as I can get a couple hours without distractions...